1. Field of the Invention
This invention generally relates to an improved method and apparatus for forming thin spiral grooves in the inner surface of metal tubing, and more particularly, to an inner grooving process and apparatus for metal tubing which tubing is suitable for heat transfer of a heat exchanger, an air conditioner, a refrigerator, or the like.
2. Description of the Prior Art
Heat exchange tubing, such as copper tubing and the like, used in an air conditioner or a refrigerator, can be provided with internal grooves to enhance the heat transfer characteristics of the tubing. Many methods and apparatus are known for forming grooves on the inside surfaces of the tubing.
Known commercial tube drawing machines and processes of producing inner grooved metal tubing include tube reducing and grooving processes wherein grooves are formed on the inner wall of metal tubing during the processing of the metal tubing after it is reduced in diameter. The inner grooves can be formed by a grooved plug or spinner mounted within the tube. However, particular difficulties have been encountered in providing an efficient method and apparatus for use in commercial drawing machines that will form internal grooves in thin wall metal tubing without rupturing the thin tubing wall.
The present inventor, Francis J. Fox, A.K.A. Francis J. Fuchs. Jr., in his U.S. Pat. Nos. 4,702,960; 4,942,751 and 4,947,669 provided improvements over the prior art in the method and apparatus for forming such internally grooved tubing. The present invention is an improvement over these and other prior art methods and apparatus.